A brand-new type of excited-state proton transfer (ESIPT) molecule based on sulfoxide/sulfenic acid tautomerism.

The excited-state proton transfer (ESIPT) behavior of organic fluorophores has attracted much attention due to their unique photophysical properties. So far, ESIPT studies have mainly focused on the transfer of hydrogen atoms between N-N, N-O, or O-O. In this work, a brand-new type of ESIPT molecule based on sulfoxide/sulfenic acid tautomerism has been thoroughly investigated.

Regioselective synthesis of 3-nitroindoles under non-acidic and non-metallic conditions.

An electrophilic substitution reaction, without acid and metal, of indole with ammonium tetramethylnitrate for accessing 3-nitroindole has been developed. In this protocol, trifluoroacetyl nitrate (CFCOONO) was produced by metathesis of ammonium tetramethyl nitrate and trifluoroacetic anhydride at sub-room temperature. Trifluoroacetyl nitrate (CFCOONO) is an electrophilic nitrating agent for a variety of indoles, aromatic and heterocyclic aromaticity.

A methyl-shield strategy enables efficient blue thermally activated delayed fluorescence hosts for high-performance fluorescent OLEDs.

Here, we report a novel methyl-shield strategy to design ideal TADF hosts for the improvement of the performance of TSF-OLEDs. The methyl group on the xanthone acceptor acts like a shield to protect the luminance center from close intermolecular hydrogen bonding with adjacent molecules, thus alleviating exciton quenching, and meanwhile the small size of the methyl group almost does not disturb the π-π stacking between acceptors, thus maintaining fast electron-transport pathways. dMeACRXTO having two methyl shields is exploited as the host to achieve a record-high EQE of 32.

Mechanically induced single-molecule white-light emission of excited-state intramolecular proton transfer (ESIPT) materials.

Described herein is the first example of mechanically induced single-molecule white-light emission based on excited-state intramolecular proton transfer (ESIPT) materials. The mechanism of mechanochromism is clearly disclosed by powder and single crystal X-ray diffraction (XRD) data, infrared spectroscopy, and fluorescence up-conversion measurement, etc. 2-(2'-Hydroxyphenyl)oxazole (6b) with a herringbone packing motif exhibits a predominant keto-form emission, giving off yellowish-green fluorescence.

"H-Type" Like Constructed Dimer: Another Way to Enhance the Thermally Activated Delayed Fluorescence Effect.

Thermally activated delayed fluorescence (TADF) materials are an essential part of TADF-based organic light-emitting diodes (OLEDs). All the reported methods to improve the performance of TADF materials were focused on achieving a high reverse intersystem crossing rate () and oscillator strength (), but most of them were studies on single molecular states. In this paper, we have discovered a new dimer architecture called the "H-type" like dimer and proved that the "H-type" like dimer is another way to improve the performance of TADF materials by calculation and experiment.

Build-up of double carbohelicenes using nitroarenes: dual role of the nitro functionality as an activating and leaving group.

The construction of double carbohelicenes is highly fascinating yet challenging work. Disclosed herein is a streamlined and simplified synthetic route to double carbohelicenes starting from nitroarenes through sequential nitro-activated -C-H arylation, denitrative alkenylation and intramolecular cyclodehydrogenation. In this synthetic strategy, the nitro group plays a dual role namely as a leaving group for the denitrative alkenylation and as an activating group for -C-H arylation, which is distinct from those of aryl halides in a conventional coupling reaction.

Synthesis of Imidazole-Based [30]Heptaphyrin and Stable Figure-Eight [60]Tetradecaphyrins via [5 + 2] Condensations in One Pot.

Derived from a Pd-catalyzed oxidative C-H/C-H coupling reaction, two giant imidazole-based [60]tetradecaphyrins adopting stable figure-eight geometry together with one [30]heptaphyrin are obtained by [5 + 2] MacDonald condensations in one pot. The directional imidazole is believed to play a vital role for the diverse cyclization and conformation stabilization.

Triazolotriazine-based thermally activated delayed fluorescence materials for highly efficient fluorescent organic light-emitting diodes (TSF-OLEDs).

Thermally activated delayed fluorescence (TADF) sensitized fluorescent organic light-emitting diodes (TSF-OLEDs) have shown great potential for the realization of high efficiency with low efficiency roll-off and good color purity. However, the superior examples of TSF-OLEDs are still limited up to now. Herein, a trade-off strategy is presented for designing efficient TADF materials and achieving high-performance TSF-OLEDs via the construction of a new type of triazolotriazine (TAZTRZ) acceptor.

Hydrogen bond modulation in 1,10-phenanthroline derivatives for versatile electron transport materials with high thermal stability, large electron mobility and excellent n-doping ability.

4,7-Bisphenyl-1,10-phenanthroline (BPhen) is a promising electron transport material (ETM) and has been widely used in organic light-emitting diodes (OLEDs) because of the large electron mobility and easy fabrication process. However, its low glass transition temperature would lead to poor device stability. In the past decades, various attempts have been carried out to improve its thermal stability though always be accomplished by the reduced electron mobility.

Molecular Design of Non-doped OLEDs Based on a Twisted Heptagonal Acceptor: A Delicate Balance between Rigidity and Rotatability.

The development of efficient non-doped organic light-emitting diodes (OLEDs) is highly desired but very challenging because of a severe aggregation-caused quenching effect. Herein, we present a heptagonal diimide acceptor (BPI), which can restrict excessive intramolecular rotation and inhibit close intermolecular π-π stacking due to well-balanced rigidity and rotatability of heptagonal structure. The BPI-based luminogen (DMAC-BPI) shows significant aggregation-induced delayed florescence with an extremely high photoluminescence quantum yield (95.

An unusual [4 + 2] fusion strategy to forge /-heteroarene-fused (quinoidal) porphyrins with intense near-infrared Q-bands.

Here we present a divergent synthesis of brand-new types of /-heteroarene-fused (quinoidal) porphyrins through Rh-catalyzed β-C-H activation/annulation of 5,15-dioxoporphyrins and dioxime derivatives with alkynes, in which the synthetic disconnections are difficult to access through the commonly used intramolecular cyclization strategy. Using the -methyl oxime as a traceless oxidizing directing group, the -embedded pyridine-fused -quinoidal porphyrin and pyridinium-fused cation are formed with controllable chemoselectivity and complete -selectivity. Replacing the exocyclic oxime with a carbonyl group delivers the pyran-fused porphyrin , achieving structural conversion from a quinoidal conformation to a stable porphyrin macrocycle.

Making silver a stronger n-dopant than cesium via in situ coordination reaction for organic electronics.

N-doping is an effective way to increase the electron conductivity of organic semiconductors and achieve ohmic cathode contacts in organic electronics. To avoid the use of difficult-to-handle highly reactive n-dopants, air-stable precursors are widely used nowadays, which could decompose to release reactive species in a subtractive way though always with unwanted and even harmful byproducts during processing. Here, we show that air-stable metals, such as copper, silver and gold, could release free electrons readily in the presence of chelating ligands, as the irreversible coordination reaction between metal ions and the ligands would push the equilibrium between metals and metal ions to the forward direction.

Synthesis of a Double-Helical Naphthotetraindole Core via an Intramolecular Dehydrogenative Homocoupling Reaction.

A novel naphthotetraindole (NTI) core was synthesized in two steps via the McMurry reaction and a [Cu]/[Ag]-promoted intramolecular dehydrogenative homocoupling reaction. NTI shows a unique X-shaped double-helical structure as determined by single-crystal X-ray diffraction analysis. The hole-transport mobility of the bare NTI core was measured to be 2.

Zn(II)-dipicolylamine-based metallo-lipids as novel non-viral gene vectors.

In this study, a series of Zn(II)-dipicolylamine (Zn-DPA) based cationic lipids bearing different hydrophobic tails (long chains, α-tocopherol, cholesterol or diosgenin) were synthesized. Structure-activity relationship (SAR) of these lipids was studied in detail by investigating the effects of several structural aspects including the type of hydrophobic tails, the chain length and saturation degree. In addition, several assays were used to study their interactions with plasmid DNA, and results reveal that these lipids could condense DNA into nanosized particles with appropriate size and zeta-potentials.

Biodegradable Poly(Amino Ester) with Aromatic Backbone as Efficient Nonviral Gene Delivery Vectors.

The development of gene delivery vectors with high efficiency and biocompatibility is one of the critical points of gene therapy. Two biodegradable poly(amino ester)s were synthesized via ring-opening polymerization between low molecular weight (LMW) PEI and diepoxide. The molecular weights of poly(amino ester)s were measured by GPC.

pH and reduction dual-responsive dipeptide cationic lipids with α-tocopherol hydrophobic tail for efficient gene delivery.

A series of tocopherol-based cationic lipid 3a-3f bearing a pH-sensitive imidazole moiety in the dipeptide headgroup and a reduction-responsive disulfide linkage were designed and synthesized. Acid-base titration of these lipids showed good buffering capacities. The liposomes formed from 3 and co-lipid 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) could efficiently bind and condense DNA into nanoparticles.

Lipoic acid functionalized amino acids cationic lipids as gene vectors.

A series of reducible cationic lipids 4a-4f with different amino acid polar-head groups were prepared. The novel lipid contains a hydrophobic lipoic acid (LA) moiety, which can be reduced under reductive conditions to release of the encapsulated plasmid DNA. The particle size, zeta potential and cellular uptake of lipoplexes formed with DNA, as well as the transfection efficacy (TE) were characterized.

Reducible Amino Acid Based Cationic Lipids as Highly Efficient and Serum-Tolerant Gene Vectors.

In this study, two cationic lipids, each containing an α-tocopherol moiety and a biocompatible amino acid headgroup (histidine or lysine) linked through a biodegradable disulfide and carbamate bond, were prepared and evaluated in cell culture as nonviral gene delivery vectors. The physicochemical properties of these lipids, including size, zeta potential and cellular uptake of the lipoplexes formed with DNA, as well as the transfection efficacy (TE), were investigated. The results show that the chemical structure of the cationic headgroup affects the physicochemical parameters of these amino acid based lipids and especially the TE.

Charge-switching amino acids-based cationic lipids for efficient gene delivery.

A series of charge-switching amino acids-based cationic lipids 4a-4e bearing a benzyl ester at the terminus of the acyl chain, but differing in the polar-head group were prepared. The physicochemical properties of these lipids, including size, zeta potential and cellular uptake of the lipoplexes formed from with DNA, as well as the transfection efficiency (TE), were investigated. The results showed that the chemical structure of the cationic head-group clearly affects the physicochemical parameters of the amino acid-based lipids and especially the TE.

Amino acid-based cationic lipids with α-tocopherol hydrophobic tail for efficient gene delivery.

In this work, three amino acid-based cationic lipids L1-L3 bearing the same α-tocopherol moiety and biodegradable ester bond linkage, but differing in the polar head-group, were prepared and applied as non-viral gene delivery vectors. The physicochemical properties such as size, zeta-potential, stability, and cellular uptake of the lipoplexes formed from lipids L1-L3 as well as the transfection efficacy (TE) were investigated. The results showed that the chemical composition of the cationic head-group clearly affects the physicochemical parameters of the amino acid-based lipids, especially the TE.